/Engine/Source/Runtime/Experimental/GeometryCollectionEngine/Public/GeometryCollection/GeometryCollectionObject.h
Find or add a auto instance mesh from a mesh and alist of material and return its index
int32 FindOrAddAutoInstanceMesh ( const [UStaticMesh](API\Runtime\Engine\Engine\UStaticMesh) * StaticMesh, const [TArray](API\Runtime\Core\Containers\TArray)< [UMaterialInterface](API\Runtime\Engine\Materials\UMaterialInterface) * > & Materials )